Range finder



Juiy 16,1946. E LAND I I 2,404,301

' RANGE FINDER Filed Mafch 2, 1945 FIG. 5 r 32 IN TOR. I

Patented July 16, 1946 RANGE FINDER Edwin H. Land, Cambridge, Mass assignor to Polaroid Corporation, Cambridge, Mass, a corporation of Delaware Application March 2, 1943, Serial No. 477,707

10 Claims. 1

This invention relates to a new and improved range finder and reticles therefor.

It is one object of the invention to provide a range finder comprising means for impressing optical indicia upon the field of view at a predetermined apparent distance from the instrument and thereby determining the distanc of objects in said field from the observer.

Another object is to provide a range finder of the above characteristics wherein a plurality of optical indicia are impressed upon the field of view, each at predetermined different apparent distances from the instrument.

A further object is to provide a range finder of the above characteristics wherein the desired op,- tical indicia are produced b means of a collimating lens and reticle means comprising one or more indicia marks each positioned in predeter- Other objects and advantages will in part be apparent and in part be pointed out in the course of the following description of one or more embodiments of the invention, which are given as non-limiting examples, in connection with the accompanying drawing, in which:

Figure l is a plan view of a housing, suitable for a range finder constituting an embodiment of the invention;

Fig. 2 illustrates diagrammatically and in plan the optical elements employed in one embodiment of the invention;

Fig. 3 is an enlarged, diagrammatic front'view.

illustrating an embodiment of the reticle means of the present invention; 7

Fig. 4 is a similar side view of the reticle means shown in Fig. 3; and

Fig, 5 is a side view, similar to Fig. 2, illustrating diagrammatically a modification of the inve'ntion.

In the form of the invention illustrated in the. drawing, housing ID of any desired size and shape is provided with a pair of mirrors or other reflecting surfaces I2 adapted to receive light from in front of the instrument throughthe windows or apertures at I 4. This arrangement serves both to provide an effectively enIa gedinter ocular distance or increased stereoscopic effect; and. also to limit the field of view to an area substantially. in front of the instrument. Associated with mirrors I2 is a pair of transparent mir- I rors I5 each of which is adapted to receive light.- from one of mirrors I2 and to reflect it towards one of eyepieceslfi. p j An observer employing this rang'e fin'der will look simultaneously through both of ,ey'epieees .I 6

with the result thathis right ye will receivev light from right-hand mirrors I2 and I5, and his left; eye will simultaneously receivelight from leftj hand mirrors I2 and I5. Itis to, be understood that mirrors I5 andmirrors I2 shouldbe sopositioned as to enable an. observer employing the instrument to seesubstantiallylthe same field with each eye. Such a structure; exceptiforthe. use of transparent mirrors ,I5 finsteadofjwholly, reflecting surfaces, is standard in the construe; tion of range finders of the class of the present invention. Its effect and purpose is toincrease the efiectiveinterocular distance of theobserver. by the distance between mirrors ,I 2, and1thus t'o increas considerably the stereoscopic acuity ,of his vision as applied to thefield;

The indicia-formingapparatus of this embodiment of the invention is illustrated in .detail in" Figs. 2, 3 and 4, and may conveniently belocated Within an extended portion I8of housing I0. it comprises a reticle 20 of particular characterise tics to be described in detail hereinaftenj alight source 22 of any desired type anda rela'tively large lens 24 or other device for collimating 'the", rays emanating from sourc 22 and traversing, reticle 29. The term i'etic1eas it isused hriri; and in the claims is to bev understood as having the meaning commonl accorded thereto in ,the. range finder art, and it is to 'be considered including any means in the optical systemof the instrument for producing visible indiciasuch, 'for example, as a line, a dot or a circle or other figure.

In a simple embodiment of the present inven-.

tion, the reticle means may comprise simply light 1 source 22, which, will preferably, comprise averti cal line filament illuminated from a suitable source of current (not shown). In this err1bodi-; ment of the invention, light source 22 will prefer ably be positioned within the fccalplane of lens 24. e The relation of its position to the focal plane of the lens will determine its'apparent distance; from the observer when it is viewed through eye;v Pieces I6. Itis. believed that the reason for this effect will be readil apparent. If the, light.

source orreticle is positioned atthe .f ocal'plane of lens 24, the rays from the reticle to eyepieces It will all be rendered parallel, and,thejresult will be to cause thereticle image to appear to lie 2,404,30 it r hat infinity. If, however, the reticle ispositioned within the focal plane of the lens, the rays going to each of eyepieces It will diverge slightly from parallelism, with the result that the reticle image tion willprovide only a single indicia in space. i i 1 For preferred results, however, there should bea: plurality of such indicia, each caused to lie at a different apparent distance from" the observer, This effect may be attained b the use of the reticle shown in greater detail in Figs. 3 and 4,

which comprises a pluralit of sheets 25, 2s, '25

requirements thereof are fulfilled if only a'single I mark is used.

Reticles of the type shown in Figs. 3'and 4 may be constructed in a Variety of ways. For example, each of sheets 25-39 may comprise a separate sheet of glass or other transparent material such as a transparent plastic having an opaque mark reproduced on one surface thereof. The converse of this construction may also housed, and each reticlemark maycomprise a light-transmitting areaetched or otherwise produced in an opaque area of one of sheets 25-30, provided that said opaque areasdo not overlap so far as to: cover the reticle mark on any of the others of said sheets. It has been found particularly useful to-preparesuch vreticles by conventional photographieprocesses, that is to say, each of the sheets25'30 may comprise a positive or negaand 30, each bearing on a surface thereof a" reticle mark A, B, C and D.

, In this embodiment of the invention, reticle 2 9 willjbe positioned. in predetermined relation to the focal plane of lens 24. For example, reticle may besopositioned that mark A of sheet 39,

will lie substantially in the focal plane, of the lens. Marks B, C and D will therefore lie at different distances .within the focal plane of the lens.-

- With reticle 20 in this position when the observer lookslthrough eyepieces [6, mark A will appear to lie the farthest-away, while mark D will appear .close .to the observer, mark C. the next, andmarkjB between mark- C and mark A..

It will. befunderstood that the relative di's tances .between I the indicia-carrying surfaces of sheets/ 30 will be such that .saidseries of in-.-

dicia will appear tolie at known distances from the instrument. -,Saiddistances may in turn be determined in a variety of ways- In the above, example-litis assumed that mirrors l5 are at; right angles to each. other and parallel to their 7 associated mirrors .l 2, In such case mark A will apparent'positions being dependent in each case upon..the .base, line of the device, i. e., the dis-- tance between mirrors l2. Similar Variation may beobtaintedbyadjusting reticle 28 with respect totheqfocal. plane offlens 24. For example,

reticle20 may be positioned with markB in the set'atan. angle of lessthan QOdegrees to each other. such that mark A will appear to lie at inw j finitywithrespectto the field. If said'angle is further-reduced below degrees, all said marks so? focal length of eighteen inches. -If reticle Zllbe tivereproductio-n of the diamond outline illustrated as forming A, B, C and D. The thickness of each sheets 25-30 will be chosen to provide the desired differences in the 1 apparent positions of the indicia thereon when viewed as illustrated in, Fig. 2. It will be apparent that said distances will vary depending upon the focal length of lens 24. and on the base line of the instrument, i. e. the distance between mirrors I2. I

As an illustrative example, assume that reticle 20 is incorporated in an instrument having a base line of four feet-and using a-lens 24 having-a so positionedwith. respect to the ,focal'point of the lens that mark D appears to lie 600 yards from the instrument, and if sheet 25 is approximately .0075 inchin thickness, mark'C will appearv to lie at 1,200 yards from the instrument;

If the baseline is increased without otherwise changing .the design, each mark will appear to he still farther away and still farther apart from each other, andthe converse will be true if the base .line. is lessened. 7, These conditions, how- 1 ever, 'will be readily understood by those skilled as. focal plane of lens, and if mirrors '15 are at right angles to each. other, mirrors i2 ,may' be i will appear to move still-nearer tothe observer. 7 All such modifications are accordingly to be con-,

strued-as coming within the scope of -the in vention.'i V

brated that the series of indicia will appear to lie -atknown. distances from the instrument; v 7 observer usingthe device may then compute the approximate distance of objects. in the fieldby It will now be understood that in all cases the rangeifinder. of the" inventionf will be so call in the art,- and need only be taken 'into' account inthe final design and calibration of the instrumentr Range finders of the type of the present invention utilizing: reticles 'of the type illustrated in example, it may be assumed that a range finder using reticle 20 is installed in a tank or airplane approaching a target, and that it is desired tohold fire until the range is, for example 200 yards. In this case reticle 20 will be so designed and positioned'with respect to the base lin of the instrument and focal length of lens 24 that mark D will appear to lie at 200 yards. Similarly, mark C may appear to lie at 300 yards, and mark B may appear to lie att400 yards. Therefore, as the tank or plane approaches the target, the gunner will known that he should prepare to fire when the apparent position of when the apparent position of' mark C coincides with the target, and should fire when the apget. As another exampla'it is particularly useful inanairplane to outline only a single mark in' j An 7 15;, "i It will be understood that the a ove-ass n e reticle 20 whose apparent position will lie at the present invention will be readily thoseskilled in the art.

parent position of mark D coincides with the-tarknown rangewhich is the maximum for accurate fire of the plane's guns.

of useful installations for the range finder of the, apparent to.

Many other examples they approach the eyes of the observer.

embodiment'of the inventionis given. only, by way of illustration, and that it maybe modified to a considerable degree without, departing. from within the scope of the invention. To a considerable extent-the construction of the range finders of the invention is determined by the pur-' pose for which they are intended. For-example, mirrors l2 and I5 are used as illustrated in Figs. 1 and 2 for the purpose. ofincreasi-ng the range of the instrument and its accuracyfat increased. ranges. However, this construction maybe modified if: the instrument is designed for use at relatively shorter ranges, i. e. ,of, the' order of. 100 yards or less. Forsuch'short ranges it. may bedesirable to rely only upon the human inter,- ocular, and Fig, 5 illustrates diagrammatically a modification of the invention suitable forjsuch use. One eye of the observer is indicated at'50' as viewing the field through a single transparent.

mirror 52, and the reticle; system comprises-light source 54, .reticle .55, and. lens .56. Mannoth r modifications will doubtless lie-apparent, to'jthose skilled in theart, and are to be construed as coming within the scope of the invention. 7

It is to be noted that light proceeding from any reticle means such as alight source or filament thereof or an indicia mark located in the focal plane of lens 24 will be collimated while if such light source or filament or indicia mark is located inside of the focal plane, that is nearer an observer than the focal plane, the lens will not bring the light rays into collimation or paralellism but will leave themslightly divergent as This is a physical characteristic of any collimator lens and throughout the specification and claims the term collimator lens is intended to have a meaning which embraces this characteristic.

It is also to be understood that the following claims are intended to cover all the generic and specific features of the invention herein described, and all statements of the scope of the. invention which, as a matter of language, might be said to fall therebetween.

What is claimed is: r

1. In a binocular range finder, in combination, a reticle comprising a plurality of indicia, a collimating lens positioned between said reticle and the eyes of an observer, means for superimposing a single image of said reticle upon the field of view, said image being at all times visible to both eyes of an observer, and means for so positioning said reticle with respect to said lens that each of said indicia is positioned a predetermined different distance from the focal plane of said lens, the apparent position of said image in said field of view being a function of the distance between said reticle and thefocal plane of said lens.

2. In a binocular range finder, in combination;

a reticle comprising a plurality of indicia, a collimating lens positioned between said reticle and the eyes of an observer, means for superimposing a single image ,of said reticle upon. the field of view, said image being at all times visible to both eyes of an observer, and means for so positioning said reticle with respect to said lens that each s. In: a binocular range nu es-1n combination:

a reticleieomprisinga pluralityof iHdiQiBmlflfGOI-f limating lens positioned between said reticle andthe eyes of an observer, means for superimposing a single image of said-reticle'upon the fieldaof; view, said-image being. at alltimes visiblesto'both eyes of an observer, and means for so positioning said reticle with respectto'saidlens: that ieach of said indicia is positioneda-predetermined' di-f,--

ferent distance from the focal plane of said lens.

said reticle comprising a plurality of superimposed 'sheets, each of said 'sheets bearing.a-n-aine dicium, saidsheets being o positionedvthat theaxis of said lens. is substantially normal thereto,

the apparent position of said image in said field of view being afunction of the distance between.

I said reticleiand the focal plane of said lens. 5:15

'4. 'Ina binocularrange finder, incombi'nation, i

a reticlecomp'rising mean providing a plurality of spaced, unconnectd indicia, a collimating lens positioned between. said reticle and 'thereye i-of an observer, means for superimposing a. single image: of saidreticle uponthe field of viewl,=;said,

image beingatall times visible to both eyes-ofan observer, and'means for 'so positioning aid reticle with respect to said lens that each of aid indicia is positioned a predetermined different distance from the focal plane of said lens, the apparent position of said image in said field of view being a function of the distance between said reticle and'the focal plane of said lens.

5. In a binocular range finder, in combination, a reticle comprising a plurality of indicia, a collimating lens positioned between said reticle and the eyes of an observer, means for superimposing a single image of said reticle upon the field of view, said image being at all times visible to both eyes of an observer, and means for so positioning said reticle with ,respectto said lens that each of said indicia is positioned a predetermined diiferv '6. In a binocular range finder, in combination,

a reticle comprising a plurality of indicia, a collimating lens positioned between said reticle and the eyes of an observer, means for superimposing a single image of said reticle upon the field of view, said image being at all times visible to both eyes of an observer, and means for so positioning said reticle with respect to said lens that each of said indicia is positioned a predetermined different distance from the focal plane of said lens, said reticle comprising a plurality of superimposed sheets, each of said sheet bearing an indicium, there being not more than one indicium on the contacting surfaces of any two sheets, the apparent position of said image in said field of view being a function of the distance between said reticle and the focal plane of said lens.

7. In a binocular range finder, in combination, a reticle, a collimating lens positioned between said reticle and the eyes of an observer, means for superimposing a single image of said reticle upon the field of view, said image being at all time visible to both eyes of an observer, and means for predeterminedly positioning said reticle with respect tothe focal plane of said lens to determine the apparent position of said reticle image within said field of view.

8. Ina binocularrange finder, in combination,

c a reticle comprising a plurality'of .indicia, a. collimating lens positioned betweem said reticl andthe eyes of an observer, transparent mirror means for superimposing a single image of aid reticle upon the field of View, said image being at all timesvisible to both eyes, of an observer, and means for so positioning said reticle with respect to said lens that-each of said indici'a is positioned a predetermined difierent distance from the focal plane of said lens, the apparentiposition of said image'in said field of view being a function of thedistance'betw'een said reticle and the-focal plane of'saidlens." 1 b 1 9. In a binocularsrange finder, zini'combination, a reticlecomprisinga plurality oflindicia," acollimating lens positioned between" said -reticle and the eyesof an observer, 'means for increasing the effective interocular .o'f an'observer, *rneans for superimposing a single-image of said reticle upon the "field of View, said -image being at all times 8 plane- 0f said lens,-the-apparent position of said image-in said field of viewebeing a fu'nctionof the distance between said reticle and' the -focal planeofsaidlen's.

10;"In a binocular range finder, incombination, V

a reticle comprising 'aiplurality of indiciaga'coh limating lens positioned between said reticle and the eyes of an observer, means for increasing-the efiective interocularsofan observer and for superimposing a single image of said reticIe'upO'n the field of-view; said image being at all times visible to'both eyes'of an observer; said means ecmpna a -filnction of th'e'dis'tance between said reti'le and the' focal plane of said'lens: g"

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